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Molecular clues to long-term memory storage

14 Jan 2020

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A new study could shed light on the molecular changes behind the memory storage process – specifically in a type of hardwired long-term memory.

Neuroscience Professor Ronald Davis, Scripps Research in the US – found that moving memories to long-term storage involves the interplay of multiple genes, a known group whose activity must be upregulated, and, unexpectedly, another gatekeeping gene set known as Ras. If either Ras or its downstream connector Raf are silenced, long-term memory storage is eliminated, the team writes in the Proceedings of the National Academies of Sciences.

Nathaniel Noyes, PhD, a research associate in the Davis lab, said: “We believe that dopamine signals to the brain that this memory is important enough to be stored long-term. We speculate that Ras and Raf receive this dopamine signal and thereby block intermediate memory and promote PSD long-term memory.”

The team’s experiments involved exposing flies to certain odours in one section of a glass tube while simultaneously administering a foot-shock. Flies’ subsequent avoidant behavior on exposure to that odour indicated their recollection of the unpleasant shock. Regardless of how many times the flies were “trained,” lowering expression of Ras and Raf reduced their long-term memory performance.

While the Ras enzyme, Ras85D, was already known for its roles in organ development and cancer, the studies suggest that in the adult brain, it apparently plays memory gatekeeper, helping direct whether experiences should be remembered as intermediate memory that dissipates after a time, or as long-term “protein-synthesis dependent” memory that persists.

How this “intermediate” memory system works in humans requires further study.